Method and apparatus for vapor deposition

ABSTRACT

A METHOD AND APPARATUS ARE DESCRIBED FOR FEEDING WIRE INTO A VAPOR SOURCE CRUCIBLE IN A VACUUM DEPOSITION SYSTEM TO EITHER REPLENISH MATERIAL VAPORIZED IN THE CRUICBLE OR TO PRODUCE A UNIFORM COATING ON THE WIRE. THE WIRE IS URGED INTO THE CRUCIBLE THROUGH A HEATED GUIDE MEMBER UPON WHICH VAPOR WILL NOT CONDENSE AND SOLIDIFY.

H. R. SMITH, JR

METHOD AND APPARATUS FOR VAPOR DEPOSITION Feb. 9, 1971 4 Sheets-Sheet 1Filed April 24 1968 Feb, 9, 1971 H. R. SMITH, JR

7 METHOD AND APPARATUS FOR VAPOR DEPQSITION 4 SheetsSheet 2 Filed April24.

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METHOD AND APPARATUS FOR VAPOR DEPOSITION Filed April 24, 1968 4Sheets-Sheet s JD v M z Q 4 5 w w W) T 13 v \I\ g 6/ I R X /5 Ii 45 22 71 \\\\W\ Y/VF Feb. 9, 1971 HI R. SMITH, JR 3,562,002

METHOD AND APPARATUS FOR VAPOR DEPOSITION Filed April 24, 1968 4Sheets-Sheet 4 NON I III ,IIIIIIIIIIIE QOE HUGH SJI'T H JR.

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United States Patent US. Cl. 11793.3 14 Claims ABSTRACT OF THEDISCLOSURE A method and apparatus are described for feeding wire into avapor source crucible in a vacuum deposition system to either replenishmaterial vaporized in the crucible or to produce a uniform coating onthe wire. The wire is urged into the crucible through a heated guidemember upon which vapor will not condense and solidify.

This invention relates to the feeding of wire into vapor sourcecrucibles in vacuum deposition systems. More particularly, the inventionrelates to an improved method and apparatus for feeding wire into avapor source crucible in such a system either to replenish materialvaporized in the crucible or to produce a uniform coating on the wire.This application is a continuation-in-part of application Ser. No.637,386, filed May 10, 1967, now abandoned.

Vacuum deposition systems generally involve the condensation of a vaporof one material on a substrate of another material, performed in arelatively high vacuum environment. The materials may be of varioustypes, such as metals and ceramics, and the substrate may be of any of avariety of thicknesses. The process may operate on a substratecomprising a continuously moving film, or the substrate may be of a morediscrete form.

In a vacuum deposition system, the vapor is often produced by utilizinga crucible containing charge material which is melted and vaporized byhigh energy electron beams directed through the open end of the crucibleand against the charge material. The production of vapor by such meansprovides good control over the thickness, density, and uniformity of thedeposited vapor and also facilitates efiicient utilization of materials.

For extended periods of operation, it is necessary to replenish thecharge material which is vaporized in the crucible. One method ofmaterial replenishment or feeding is by placing batches of the chargematerial in solid form into the crucible through the open end thereof.Such a feeding method is not sufliciently sophisticated for manyoperations in that it usually necessitates interruption of the vapordeposition process.

Another method of feeding is by inserting a continuously moving rod orwire of the charge material through the open mouth of the crucible. (Inthis specification and claims, the term wire is intended to include apiece of elongated slender metal or non-metal of circular cross sectionand, in addition, any elongated form of metallic or non-metallicmaterial of circular or non-circular cross section, such as an elongatedrod or tube.) In wire feeding apparatus, the wire moves into thecrucible at a rate just suiiicient to supply losses of the chargematerial due to vaporization. Although this type of feeding avoids anynecessity for interrupting the process, certain difficulties may arisein that, due to the high heat of the crucible, the wire may melt toosoon. When this happens, the molten drops may not enter the crucible inthe proper place to replenish the molten charge, but instead may fallout of the crucible or may solidify on cool parts of the crucible iceaway from the area of the molten charge. Early melting might also causethe wire to jam in the feeding apparatus. Another difficulty is that thefeeding apparatus, being near the open end of the crucible, mayinterfere with the vapor beam emanating from the mouth of the crucibleand become heavily coated or clogged with condensate.

In a particular type of vacuum deposition system, the crucibles arecylindrical and rotate about their axes, which are horizontallydisposed. The reason for rotating the crucible is twofold. First, aneven distribution of the melted charge material is effected about thewall of the crucible to provide a symmetrical vapor beam of even densitymoving out of the crucible mouth. Second, although the electron beam orbeams may impinge upon only a small area of the molten charge, byrotating the crucible, all of the charge is bombarded by each electronbeam with a substantially uniform transfer of energy from the beamthroughout the charge. Such a rotating crucible has particular advantagein coating vertically disposed substrates such as glass because, due tothe horizontal attitude of the crucible axis, the vapor beam emittedfrom the crucible is substantially horizontal. Two or more of suchcrucibles may be arranged in banks in a deposition system for coatingparticularly large substrates.

Bulk feeding of such crucibles has proved unsatisfactory, as hascontinuous front feeding by wire, for the difficulties mentioned in theabove discussion of these two feeding methods. Development of feedingmethods other than the two types described is further complicated due tothe fact that the crucible is rotating and, at some point in the feedprocess, a transistion must occur in the feed material from anon-rotating condition to a rotating condition.

Rotary vapor source crucibles may be used to produce a uniform coatingon wire or other elongated substrates without having to turn thesubstrate in order to expose all surfaces to the fiow of vapor from thesource. Large amounts of vapor are typically present in vapor sourcecrucibles. Accordingly, wire being fed into the crucible may undergonon-uniform and excessive coating, or excessive heating, as vaporcondenses on the wire too soon and in an irregular manner.

It is an object of this invention to provide an improved method andapparatus for feeding wire into a vapor source crucible.

Another object of the invention is to provide a method and apparatus forcontinuously feeding a charge material into a vapor source crucibleother than through the open end of the crucible.

Still another object of the invention is to provide an improved methodand apparatus for continuously feeding charge material into a rotatingcrucible.

A further object of the invention is to provide a method and apparatusfor feeding charge material in wire form into a rotating cruciblethrough an opening in a wall of the crucible.

It is another object of the invention to provide wire coating apparatusin which close regulation of wire temperature may be achieved, and inwhich non-uniform coating is avoided.

Other objects and the various features of the invention will becomeapparent to those skilled in the art from the following descriptiontaken in connection with the accompanying drawings wherein:

FIG. 1 is an elevational view of a vapor source assembly includingfeeding apparatus according to the invention;

FIG. 2 is an enlarged partially sectioned view of a portion of theassembly of FIG. 1;

FIG. 3 is a further enlarged sectional view of the crucible and aportion of the drive shaft therefor of the assembly of FIGS. 1 and 2;

FIG. 4 is a still further enlarged full section view of a portion of thevapor source assembly of FIGS. 1 and 2 at the end thereof opposite thecrucible;

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 3; and

FIG. 6 is an elevational view of apparatus of the invention as utilizedfor coating wire.

In accordance with the invention, wire is fed into a vapor sourcecrucible 11 having a guide member 12 disposed in an opening 13 in a wall14 of the crucible. The guide member has a wire conducting passage 15therethrough communicating with the interior of the crucible. The Wireis urged through the wire conducting passage into the crucible and theguide member is heated to provide a temperature at the end of the guidemember adjacent the interior of the crucible which exceeds the meltingtemperature of the material in the wire.

A flow of gas may be established through the wire conducting passage 15toward the interior of the crucible 11 to prevent vapor from enteringthe passage and condensing on portions of the guide member 12 havingtemperatures which do not exceed the condensation temperature of thematerial in the wire. Such gas flow is also advantageous during start upand shut down operations wherein the end of the guide member adjacentthe interior of the crucible may not be of a temperature exceeding themelting temperature of the material in the wire. The gas issuing fromthe passage forms a protective cloud over such end of the guide memberand inhibits condensation of vapor thereon.

In connection with apparatus utilizing a rotating vapor source crucible,the wire is fed through a hollow drive shaft 16 for'the crucible 11. Theguide member 12 is positioned such that the passage 15 therethroughcoincides with the axis of rotation of the crucible. The wire is guidedin the hollow drive shaft by an elongated nonrotating snout 17cantilevered from a supporting plate 55 of the apparatus. The snout maybe provided with coolant conduits for keeping the wire cool during itspassage through the hollow drive shaft.

Referring in more detail to the drawings, apparatus is illustrated whichis constructed in accordance with the invention, and the method of theinvention may be practiced in connection with such apparatus. Althoughthe illustrated embodiment is designed specifically for use inconnection with apparatus for vaporizing aluminum, it is to beunderstood that wire of other feed materials might also be utilized withlittle or no modification required. Moreover, although certain materialsare specified for various portions of the apparatus describedsubsequently, it is to be understood that other materials may besuitable in some circumstances.

The vapor source assembly illustrated includes a cooled crucible 11having an annular coolant flow chamber 18 in the walls thereof. Suitablebaffies, not shown, may be provided in the coolant flow chamber fordirecting coolant in a desired flow. The crucible may be constructed ofcopper and the coolant circulated may be water. The crucible is ofgenerally cylindrical shape, having an open end through which the vaporproduced in the crucible escapes in the form of a vapor beam. The rim ofthe open end of the crucible is surrounded by a lip 19 and the flowchamber 18 extends partially into the lip. The opposite end of thecylindrical crucible is closed by an end wall 14. The closed end wallincludes an inlet passage 21 and an outlet passage 22 through whichcoolant may be passed into and from, respectively, the flow chamber 18in the cylindrical crucible walls.

The closed end wall 14 of the crucible 11 has an opening 13 therein, theaxis of which is aligned with the axis of the cylindrical crucible. Theopening has two sections of different diameters, with the smaller of thetwo communicating with the interior of the crucible. The crucible issecured to a drive shaft 16 which mates in the larger section of theopening in the end wall of the crucible.

A fitting 23, which is welded to the end of the drive shaft, is suitablysecured to the end wall 14 of the crucible in the larger part of theopening 13 therein. The drive shaft extends from the crucible axiallythereof and is journalled by a plurality of bearings 24 enclosed in ahousing 25 for the source assembly. The housing for the source assemblyis supported in an opening 26 in a wall of a vacuum chamber housing 27by means of a bolted flange and O-ring vacuum seal 20.

The vapor source assembly housing 25 is provided with an appendage 28through which a power shaft 29 extends perpendicularly of the driveshaft 16. A bevel gear 31 on the power shaft engages an annular bevelgear 32 on the drive shaft for driving same. Ball bearings 33 areprovided in the appendage 28 for journalling the power shaft 29. Thehousing 25 includes a pair of annular shoulders 34 and 35 which extendinwardly toward the drive shaft and which contain seals 36 and 37 toenclose a lubricant chamber 38 for the bevel gears 31 and 32 and thebearings 24 in 'which the drive shaft is journalled. Lubricant may alsoenter the appendage 28 to lubricate bearings 33, and an annular seal 40is provided to contain lubricant in the appendage 28. Suitable means,not shown, for conducting lubricant to and from the chamber may beprovided.

The drive shaft 16 is constructed with two coolant flow passages 39 and41 therein which extend along the drive shaft between the outer surfaceand the axis thereof. Each of the passages is slightly less thansemi-annular in cross section and one of the passages 39 carries coolantto the crucible while the other 41 carries coolant from the crucible.The passages in the drive shaft communicate with the inlet and outletpassages 21 and 22 in the crucible 11 through suitable openings 42 and43 near the crucible end of the drive shaft.

Coolant is supplied to the coolant flow passages in the drive shaftthrough a coolant inlet conduit 44 in the vapor source assembly housing25. The coolant inlet conduit communicates with an annular coolant inletchamber 45 formed between the inwardly projecting annular shoulder 35 inthe housing and a further inwardly projecting annular shoulder 46.Shoulder 46 is sealed against the outer periphery of the drive shaft bya seal 47. Coolant under pressure in chamber 45 enters passage 39 in therotating drive shaft 16 through an opening 53. v

A further annular shoulder 48 projects inwardly from the housing 25 nearthe rearward end of the drive shaft and is sealed by seals 49 againstthe outer periphery of the drive shaft. This shoulder 48, together withthe previously mentioned shoulder 46, forms an outlet chamber 51 for thecoolant. Coolant returning from crucible 11 through passage 41 enterschamber 51 through an opening 54 in the drive shaft. A coolant outletconduit 52 in the vapor source assembly housing communicates with theoutlet chamber to remove coolant therefrom for disposal orrecirculation.

Thus, coolant enters the inlet chamber 45 through the inlet conduit 44flows through the opening 53 in the outer wall of the drive shaft 16,through the coolant conducting passage 39 therein, through the opening42 and coolant conducting passage 21, into flow chamber 18 in thecrucible 11. Coolant flowing back from flow chamber 18 enters thecoolant conducting passage 41 in the drive shaft through passage 22 andopening 43. The returning coolant then flows rearwardly along the driveshaft through the outlet opening 54 in the drive shaft into the outletchamber 51, and from there through the outlet conduit 52. This coolantflow is maintained while the drive shaft and crucible are rotating at arelatively high speed. The drive shaft, being hollowed and therebyproviding direct communication with the interior of vacuum housing 27,must therefore be vacuum sealed at its rearward end. This isaccomplished by seals 49 and by a sealing plate 55 secured over the openrear portion of the vapor source assembly housing 25.

In vapor depositing aluminum, insulation between the cooled walls of thecrucible 11, which may be copper, and the molten aluminum contained inthe crucible may be provided by a layer of tungsten sheet 56. The innersurface 57 of the tungsten sheet is sprayed with zirconium oxide toprovide good thermal insulation and to prevent chemical reaction betweenthe highly reactive molten aluminum and the tungsten. To further insurethis, zirconium may be melted into the crucible prior to placingaluminum therein such that, when the vapor source is in full operation alayer of molten zirconium-aluminum alloy is disposed in the melt 60between the molten aluminum in the melt near its surface and thetungsten sheet. This also provides superior thermal insulation betweenthe relatively cool walls of the crucible and the high temperaturemolten aluminum.

The charge material in the crucible 11 is melted by one or more highenergy electron beams directed into the crucible through the open endthereof to impinge on the surface of the charge material. The beams areproduced by one or more electron beam guns 59 which are mounted invacuum chamber housing 27. Guns 59 may be of a type known in the art andpreferably have provision for varying the intensity and direction of theelectron beams (indicated by the dotted lines) which they produce. Thecharge, when molten, is held by centrifugal force against the inner sideof the cylindrical walls of the crucible.

In order to replenish the aluminum charge material which is vaporized inthe crucible 11, aluminum wire is fed into the crucible to be meltedtherein. The wire enters the crucible through a refractory materialguide 12 inserted in the smaller section of the opening 13 of the closedend wall 14 of the crucible and held therein by shoulders 61 which matein bayonet type recesses in the opening. The material of which the guide12 is constructed, in the case of molten aluminum charge, should be amaterial which is not highly reactive with aluminum vapor. Asatisfactory material for this purpose is a blend of the ceramicstitanium diboride and boron nitride. The guide may be formed by mixingpowders of these ceramics and then hot pressing the mixture into thedesired shape. Naturally, for vaporizing other materials, a differentmaterial of suitable characteristics may be utilized for the guide. Agraphite block 62 is disposed just adjacent the refractory materialguide. The graphite block is held in place between the fitting 23 andthe refractory material guide to thermally isolate the fitting from theguide. The fitting, graphite block, and refractory material guide areeach provided with wire conducting passages 63, 64 and 15, respectively,each of the passages being in alignment, for passing the feed wire intothe crucible.

The feed wire is carried up the center of the hollow drive shaft 16 inan elongated guide or snout 17. The snout comprises a pair of concentriccylindrical sleeves 65 and 66 mounted at-one end to the backing plate 55of the source assembly housing 25 and cantilevered within the hollowdrive shaft 16. The end of the snout 17 adjacent the crucible isprovided with a solid block or head 67 of a material, such as copper,and the sleeves 65 and 66 of which the snout is comprised form coolantconducting passages. The head 67 is provided with an annular recess 68.Openings 69 are provided in the end of sleeve 66 to link the passagesformed by the concentric sleeves. A coolant, such as water, may bepassed through the passage formed between sleeves 65 and 66 to therecess 68 in the head, passed through openings '69, and returned throughthe sleeve 66. This maintains a cool temperature in the head and thesnout for cooling the aluminum wire. A coolant inlet conduit 71 and acoolant outlet conduit 72 are provided in sealing plate 55. Inletconduit 71 communicates with the passage between sleeves 65 and 66whereas outlet conduit 72 communicates with the interior of sleeve 66.The conduits operate, respectively, to pass coolant into and from thesnout.

The wire is carried through the snout 17 in a guide tube 76 whichcommunicates with a wire conducting passage 77 in the head 67 of thesnout. At the end opposite head 67, the guide tube 76 extends throughthe sealing plate 55 and a backing plate 75 bolted to plate 55 into aseal block 78. The guide tube may, for example, be made of stainlesssteel. The seal block 78 is contained in a seal housing 79 bolted to thebacking plate 75. The seal housing also contains a plurality of axiallyspaced rubber disc seals 81 having suitable spacing blocks 82therebetween. The spacing blocks, disc seals and seal block are all heldin place in seal housing 79 by a plug 84 threaded into the seal housingto abut the furthest left spacing block 82. Aligned passages 83 extendthrough the spacing blocks, the plug, and the seal block, and openingsare provided centrally of the seals. The openings in the seals are ofsmaller diameter than the wire. Thus, the passages in the spacing blocksand the openings in the seals permit passage of the wire through theseal housing, while the seals prevent atmosphere from passing into theguide tube and thus contaminating the vacuum in the vacuum chamberhousing 27. To further insure proper vacuum sealing, a vacuum pump-outpassage 85 is provided in the central one of spacing blocks v82.. Avacuum pumpout tube 86 is attached to the seal housing 79 andcommunicates with passage 85 so that evacuation of the passage may beattained through use of a suitable vacuum pump, not shown. A gas inletconduit 87, the purpose of which will be subsequently explained, isprovided in the seal housing 79.

Wire enters the seal housing 79 through a guide tube 88 which extendsrearwardly of the housing 79 and extends into plug 84, being axiallyaligned with the passage 83 therein. The tube 88 is supported in a snout8-9 which is an appendage of a cap 90 bolted to the seal housing Thewire is driven through the seal housing and through the guide tube 76 inthe snout into the crucible 11 by means of a capstan 91 and pinch roller92 disposed at the rearward end of the guide tube 88. A suitablestraightening device 93 may also be provided for straightening the wireprior to the wire passing between the capstan and pinch roller. The wireis drawn through the straightening device 93 and over an idler wheel 94,from a supply reel 95, The supply reel, idler wheel, straighteningdevice, capstan and pinch roller are all mounted to a suitablesupporting frame 96. A motor 97 for driving the capstan 91 through asuitable drive mechanism (not shown) is also mounted on frame 96.

In the rotating type of crucible, such as is shown in the drawings,continuous feeding of the wire through the open end of the cruciblepresents several disadvantages. The feeding apparatus may partiallyobstruct the vapor beam and may become heavily coated with condensate asa result of its proximity to the vapor beam. These problems, of course,are present in the case of non-rotating crucibles as well. A particularproblem with respect to open end feeding of rotating crucibles where theaxis of rotation is horizontal lies in the necessity for getting thewire far enough into the crucible before it melts. The high temperaturesin the crucibles, coupled with the fact that the high energy electronbeams are entering the crucible through the open end thereof, make thisextremely diflicult since the wire is inclined to melt very quickly. Ifthe wire melts too soon, the molten material may spatter out or aroundthe open end of the crucible or clog the condensing on the exposedsurface of the guide therefore merely runs off and falls back into themelt. If the crucible and, hence, the guide are rotated, centrifugalforce spins the condensed vapor radially outward of the opening in theguide. Heating of the guide occurs as a result of radiation from themolten aluminum and vapor in the crucible and from impingement thereonof some of the fringe electrons in the electron beams entering thecrucible. Control over the temperature of the guide is effected bycontrolling the direction and power of the electron beams, particularlythe direction. The beams are directed so that fringe electrons impingeupon the guide to maintain the guide at the desired temperature,consistent with the further consideration that the beams must effect thedesired heating and vaporization of the charge. If desired, the guidemay be heated to a temperature exceeding the condensation temperature ofthe aluminum vapor, thus preventing any condensation on the guide. Theguide, however, must not be heated to such a temperature as to cause arelatively high rate of reaction between the refractory material and thealuminum vapor that would erode the guide.

The guide, therefore, provides a hot surface or hot spot in a relativelycool end wall of the cooled crucible to insure that the passage throughwhich the wire is passing remains free of condensate. Only the surfaceof the guide, which is in the crucible and therefore exposed to thevapor, need exceed the vapor melting temperature. As a practical matter,however, such temperatures will exist for a given depth in the guide.Aluminum vapor is generally prevented from entering into the spacebetween the feed wire and the refractory insert and hence fromcondensing on the walls of the passage beyond the given depth by aslight flow of air through the passage due to the necessarily imperfectnature of the sealing arrangement. In addition, the moving wire willhelp to abrade any condensate from the walls of the passage. The wire ispassed through the guide at a sufficiently high rate as to preclude thepossibility of the wire melting prior to entering the crucible due toradiated and/or conducted heat from the guide. In the illustratedapparatus, the graphite block 62 adjacent the refractory guide 12prevents the fitting 23 from becoming so hot that the aluminum wirepassing through the passage therein will be melted or fused to the wallsof the passage and also helps to thermally insulate the guide from itscooler surroundings.

As the wire enters the crucible, it will proceed a certain distance andthen melt. The drops of molten material will fall down, due to theeffect of gravity, into the molten pool of the spinning crucible. Onceentering the pool, the

drops form part of the melt and are distributed evenly around the wallsof the crucible. The exact distance the wire protrudes into the cruciblebefore it melts will depend upon the temperature of the wire as itenters the crucible (due to radiation and conduction of heat through therefractory guide and the graphic block) which will depend, among otherthings, upon the feed rate of the wire. The temperature of the wire willalso depend upon the heat radiation from the molten material in thecrucible and upon the impact of the electron beams directly on the wire.The latter factor is generally the primary factor in determining theposition at which the wire will melt.

The combination of the cooled snout and the thermally isolatedrefractory guide helps to keep the Wire cool and in its solid conditionuntil it is in the proper position for melting and, in addition,prevents vapor condensation from clogging the wire conducting pasage.There will be a temperature gradient in the refractory guide whichdecreases axially from the crucible end to the graphite block end andwhich also decreases radially outward toward the water cooled crucible.As pointed out above, the surface of the refractory insert which is inthe crucible should exceed the melting temperature of aluminum in orderthat aluminum will not clog the hole.

Under certain circumstances, such as slow wire feed rates (of the orderof 25 inches per minute or less), or in the case of relatively highvapor pressures, the abrading action of the wire and the air flowthrough the passage may be of little effect. Accordingly, vapor mayenter the wire conducting passage in the guide and tend to condense onthe walls thereof, clogging the passage. To prevent this, the inventioncontemplates the establishment of a flow or bleed of a relatively inertgas, for example argon, through the passage toward the interior of thecrucible. The gas fiow into the vacuum system is selected so that thevapor pressure of the vacuum system is only raised an amount of theorder of 2/ ths of a micron of mercury. It has been found such anincrease has a negligible affect on system operation. Under someconditions, it may be possible to use higher flow rates of gas withoutdetrimental effect. The presence of the gas in and around the passagemakes it probable that the aluminum vapor particles will collide with anatom of gas and be reflected back out into the crucible before theyimpinge upon the passage wall or the wire. This prevents the vapor fromcondensing in the passage and clogging the passage.

In the apparatus illustrated in the drawnigs, the gas enters the sealingcap '55 through the inlet conduit 87 into the space between the snout 17and the drive shaft 16. The gas, since it cannot flow back out throughthe stainless steel guide tube 76 due to the rubber disc seals and thewire, finds its way through the passages 63, 64 and 15 in the fitting23, graphite block 62 and refractory guide 12, respectively, into thecrucible 11.

The gas bleed has particular application during start up and shut downoperations of the apparatus. During starting, the temperature of therefractory guide will naturally be below that of the melting temperatureof aluminum. To prevent condensation and solidification of aluminum onthe guide, such that the hole would become clogged, the gas flow isincreased to an extent such that a protective cloud of gas exists overthe surface of the guide facing into the crucible. In order to heat therefractory guide to the desired temperature, the electron beams may bedeflected slightly from their normal position such that enough electronswill bombard the guide to heat it up quickly. The beams are thenrestored to their operating position and the aluminum wire is urgedthrough the snout into the crucible and melted by the beams to build upthe molten charge. During shut down operations, the gas bleed has asimilar effect, while the refractory guide is cooling and while aluminumvapor is .still present in the crucible.

Referring now to FIG. 6, an alternative embodiment of the invention isillustrated. The apparatus of FIG. 6 is for coating wire and utilizes acrucible 111, one end thereof being open and surrounded by a lip 119.Parts similar in function to parts of the previously described apparatus,are given identical reference numbers preceded by a 1, and 'will notall be described in detail. The crucible 111 is enclosed within acylindrical vacuum enclosure 201 evacuated through a duct 202 by asuitable vacuum pump 203. Molten material is contained within an annularcoaxial recess 156 on the inner side of the crucible 111. As will beexplained, the crucible 111 is cooled in order to form a skull 157 ofthe evaporant material between the molten material 160 and the crucible111. An electron beam gun 159, of a type similar to the electron beamgun previously described, is utilized for heating the surface of themolten material in the annular recess. The electron beam produced by thegun 159 moves through an arcuate path into the crucible through the openend thereof.

The crucible 111 is supported in the enclosure 201 by a hollow driveshaft 116, the drive shaft also operating to rotate the crucible. Thedrive shaft 116 extends axially of the crucible through a wall 127 ofthe enclosure 201 into a sealed housing and bearing arrangement (notshown) identical with that previously described. The

closed end wall 121 of the crucible has an opening 113 therein, the axisof which is aligned with the axis of the crucible. The opening 113 hastwo sections of different diameters, the smaller of the twocommunicating with the interior of the crucible. The crucible is securedto the drive shaft 116 which mates in the larger section of the opening113 in the closed end wall of the crucible. A fitting 123, which iswelded to the end of the drive shaft, is suitably secured to the endwall of the receptacle in the larger part of the opening 113 therein. Adriving motor and suitable gear arrangement (also not illustrated) fordriving the shaft 116 are provided exteriorly of the enclosure 201.

The drive shaft 116 is constructed as in the previously describedapparatus, with two coolant passages 139 and 141 therein which extendalong the drive shaft between the outer surface and the axis thereof.Each of the passages is slightly less than semi-annular in crosssection. The passage 139 carries coolant to the crucible, while thepassage 141 carries coolant from the crucible. The passages in the driveshaft communicate with a coolant fiow chamber 118 in the cruciblethrough an inlet passage 121 and an outlet passage 122. Suitable meansas previously described, not illustrated, are provided exteriorly of theenclosure 201 for supplying coolant to the inlet passage 139 and forremoving coolant from the outlet passage 141 as the drive shaft 116rotates.

The wire 204 to be coated is fed into the crucible 111 as in thepreviously described embodiment. Replenishment feed stock for the moltenmaterial 160 may be fed in through the open end of the crucible asneeded. Under some circumstances, it may be desirable to maintain thewire 204 at a sufliciently low temperature prior to entry into thecrucible as to prevent excessive heating thereof. Such excessive heatingmay occur when the wire exceeds the melting temperature of the coatingmaterial, causing the coating material to run after it condenses on thewire and produce an uneven coating. Moreover, such excessive temperaturemay be reached at a reaction temperature between the wire and thecoating material, or at a temperature beyond which the wire becomes tooductile for proper handling.

In order to cool the wire 204 until just prior to its entry into thecrucible 111, the wire is passed up the hollow drive shaft 116 in a wireconducting snout 117. The snout is identical with that previouslydescribed and comprises a pair of concentric cylindrical sleeves 165 and166 suitably mounted to a support structure, not illustrated, which isfixed with respect to the rotary drive shaft. Accordingly, the snout iscantilevered within the hollow drive shaft and does not rotatetherewith. The drive shaft is vacuum sealed (not shown) to the snout asbefore described to maintain the integrity of the vacuum enclosure 201.This is necessary because the hollow interior of the drive shaftcommunicates with the interior of the crucible. The end of the snouttoward the crucible is provided with a solid block or head 167 of amaterial, such as copper, and the sleeves 165 and 166 of which the snoutis comprised form coolant conducting passages. The head 167 is providedwith an annular recess 168. Openings 169 are provided in the end of thesleeve 165 to link the passages formed by the concentric sleeves. Acoolant, such as water, may be passed through the passage formed betweenthe sleeves to the recess 168, passed through the openings 169, andreturned through the sleeve 165. This maintains a cool temperature inthe head and the snout for cooling the wire 204. Suitable inlet andoutlet ducts may be provided in the support structure, not illustrated,for the snout in order to supply the coolant to the snout.

The wire 204 is carried through the snout 117, as in the previouslydescribed apparatus, in a guide tube 176 which communicates with a wireconducting passage 177 in the head 167 of the snout. The guide tube 176and the passage 177 are aligned on the axis of the rotating crucible111. The wire is fed into the tube 176 as in the previously describedapparatus.

The wire 204 is passed through the rotary crucible 111 from the supplyreel (not shown) to a takeup reel 206. The takeup reel 206 is mounted ona bracket 207, such bracket being secured to the exterior of theenclosure 201. The wire is guided from the supply reel through the guidetube 176 in the snout 117. After passing through the crucible 111, theWire emerges from the enclosure through a suitable vacuum valve 208,passes between a pair of drive rollers 209 and around a guide roller 211to the takeup reel 206. The drive rollers 209 govern the speed of thewire and the takeup reel 206 is driven by suitable means including aslip clutch in order to take up slack in the wire. By regulating thespeed of the wire and the cooling rate in the snout, the wiretemperature may be controlled.

In order to prevent vapor from condensing on the cooled snout 117 andthereby plugging the passage 177 in the head 167, the smaller section ofthe opening 113 in the closed end wall of the crucible 111 is closed bya guide 112. The wire 204 enters the rotary crucible axially thereofthrough a small passage 115 in the center of the guide. The guide iscomprised of a suitable refractory material and is held in the wall ofthe receptacle by shoulders 161 which mate in bayonet type recesses inthe small section of the opening 113. The refractory material of whichthe guide is constructed is selected to be not highly reactive with thematerial of the wire. The guide is heated to exceed the meltingtemperature of the deposit material as in the previous embodiment,thereby preventing clogging of the passage 115.

The refractory material guide 112 is heated by the fringe electrons ofthe electron beam produced by the gun 159. If this is insufiicient,further heating may be accomplished by varying the strength of thedeflecting field of the beam to sweep the beam periodically over theguide. By maintaining the refractory material guide at a temperatureabove the melting temperature of the vapor in the crucible 111, thecoating material which condenses on the guide merely runs off. Thiskeeps the passage clear and prevents interference with the movement ofthe wire 204.

It will therefore be seen that the invention aids in effecting acontinuous feed of solid wire, such as aluminum, from a relatively coolenvironment exteriorly of the vapor source assembly crucible to theextremely hot and high vapor pressure environment of the crucible. Theinvention effects a continuous feed by providing a temperaturetransition which is smooth in order that the wire will melt at theproper time. Vapor in the crucible is prevented from condensing aroundand in the wire passage such that the passage remains free of blockage.By doing so the invention provides an improved method and apparatus forfeeding a solid evaporant material, in wire form, into a vapor sourcecrucible. The invention has particular application to those crucibleswhich are designed to rotate about horizontal axes for coating verticalsubstrates. The method and apparatus are applicable to various materialsand are not limited to use with aluminum, as described in connectionwith the specific embodiment shown. The invention is superior in manyrespects to feeding through the open end of the crucible in either acontinuous manner or by a batch feeding procedure. The invention mayalso be applied to the continuous coating of a wire substrate toregulate temperature and produce an even deposit.

Various modifications and embodiments of the invention other than thoseshown and described herein will be apparent, from the foregoingdescription, to those skilled in the art and such other modificationsand embodiments are intended to fall within the scope of the appendantclaims.

What is claimed is:

1. An apparatus for feeding wire into a rotating vapor source cruciblethrough an axial opening in a wall thereof,

such crucible being driven by a hollow drive shaft having one endsecured to the crucible around such opening, said apparatus including incombination, a support structure disposed at the end of the drive shaftopposite the cruci ble, elongated guide means secured to said supportstructure and projecting into the hollow drive shaft, said guide meanshaving a first passage therein for guiding the wire through the rotatingdrive shaft toward the crucible, a refractory guide disposed in theopening in a wall of the crucible proximate the end of said guide meansopposite said support structure, said refractory guide having a secondpassage therein aligned with said first passage and communicating withthe interior of the vapor source crucible for guiding the wire into thecrucible, and means for urging the Wire through said first and secondpassages, said refractory guide being constructed to develop atemperature at the end thereof adjacent the interior of the crucible,due to heat applied to said refractory guide from the crucible, whichexceeds the melting temperature of the material in the vapor, wherebyaccumulation of condensed vapor around the wire conducting passage isprevented to keep said wire conducting passage clear.

2. Apparatus in accordance with claim 1 wherein means are provided forestablishing a flow of gas through said second passage toward theinterior of the crucible.

3. Apparatus in accordance with claim 1 wherein said elongated guidemeans comprise a cylindrical member defining a plurality of fluidconducting passages, a solid metal tip at one end of said cylindricalmember to which said fluid conducting passages conduct coolant forcooling said tip, and an elongated sleeve defining part of said firstpassage and extending axially along said cylindrical member to said tip,said tip having a hole therein defining the remainder of said firstpassage.

4. Apparatus in accordance with claim 1 including means for withdrawingthe wire from the crucible after condensation of vapor on the wire.

5. An apparatus for feeding wire into a cooled vapor source cruciblethrough an opening in a wall thereof, including in combination, a guidemember disposed in the opening in a wall of the crucible, said guidemember having a wire guiding and conducting passage therethrough, meansfor urging wire through said wire conducting passage into the crucible,said guide member being thermally insulated from said urging means, andmeans for heating said guide member so that accumulation of condensedvapor on said guide member adjacent the wire conducting passage isprevented to keep said passage clear.

6. Apparatus in accordance with claim 1 wherein means are provided forrotating the crucible about an axis passing through the opening, wherebycondensed material in liquid form flows radially outward of the opening.

7. Apparatus in accordance with claim 1 including means for withdrawingthe wire from the crucible after condensation of vapor on the wire.

8. Apparatus in accordance with claim 1 wherein means are provided forestablishing a How of gas through said wire conducting passage towardthe interior of the crucible to prevent vapor from condensing onportions of said guide member within the wire conducting passage.

9. Apparatus in accordance with claim 8 wherein said guide member iscomprised of a refractory material.

10. A method for feeding Wire into a cooled rotary vapor source crucibleheated by at least one electron beam and having a guide member disposedin an opening in a Wall of the crucible, said guide member having a wireguiding and conducting passage therethrough lying on the axis ofrotation of the crucible, said method comprising: rotating the crucible,heating the guide member at least partially by the electron beam,controlling the electron beam to provide a temperature at the end of theguide member adjacent the interior of the crucible which exceeds themelting temperature of the material in the vapor, whereby material whichcondenses around the wire conducting passage flows radially outward bycentrifugal force to keep said wire conducting passage clear, and urgingthe wire through the wire conducting passage into the crucible at a ratesufficient to prevent melting of the wire prior to entry into thecrucible.

11. A method in accordance with claim 10 wherein the wire is the samematerial as the vapor material and is melted in the crucible toreplenish the molten material therein.

12. A method in accordance with claim 10 wherein the wire is maintainedat temperatures below the condensation temperature of the vapor materialand is drawn through the crucible at a rate which allows a desiredamount of vapor to condense on the wire.

13. A method in accordance with claim 11 wherein a flow of gas isestablished through the wire conducting passage toward the interior ofthe crucible to prevent vapor from condensing on portions of the guidemember within the wire conducting passage.

14. A method in accordance with claim 13 wherein said flow of gas isestablished prior to the steps of heating the guide member and urgingthe wire through the wire conducting passage into the crucible, and ismaintained after such heating and urging steps have been discontinued,whereby condensation of vapor which would clog the wire conductingpassage is prevented during start up and shut down operations,respectively.

References Cited UNITED STATES PATENTS 2,879,739 3/1959 Bugbee et a1.117-107X 3,019,129 3/1962 Walsh 117-101 3,360,600 12/1967 Du Bois 13-31ALFRED L. LEAVITT, Primary Examiner C. K. WEIFFENBACH, AssistantExaminer US. Cl. X.R.

